I understand what everyone is saying about “the safety features are already built in to the garage door mechanism”, but that’s just not what UL says. (So argue with them, not me.)
After over five years of review, they revised the standards for garage door controllers to distinguish between “unattended” (home automation) and traditional handheld garage door remotes.
They felt that there were additional safety issues introduced by unattended operation that were not met by the existing garage door safety features, and they specifically discussed the use of relays to control a garage door. (You will see this mentioned in the article I linked to upthread.)
Specific dangers introduced by unattended operation
Their specific concerns with a relay type system were:
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they wanted a way for someone in the garage to immediately override an instruction sent by the home automation system. So it is now part of the UL 325 standard that the button on the wall override a home automation command. That won’t happen if you just use a relay.
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they were particularly concerned about instructions which might be sent multiple times in succession even if the door had hit something when closing the first time.
Testing the scenario
Anyone who has set up a system using a non-UL listed relay can easily test this. Open the garage door. Block the pathway above or below the detection beam with something that won’t damage the door, a lot of people use toilet paper or paper towel rolls. Now close The door using the mobile app. After the door hits the towels And reverses (without ever closing all the way), wait until you see the “door open” status in the mobile app and again issue a close command. If the door goes down and hit the towels the second time, that’s a violation of the UL 325 standard.
The fear, again, is that someone might be at the office, get a notification that the door is open, hit the close button, not realize that the door was hitting an obstacle, and issue a second close command. Even worse, it is quite possible to set up an automated rule, for example one that checks to see if the door has been open for more than 10 minutes, and have the automated rule keep re-issuing the close even though the door is hitting an obstacle each time.
As I mentioned, this did happen to some community members using a relay method and the previous “ridiculously automated garage door” smart app.
Managing the Message Traffic
Neither of these two points will be addressed by the existing safety features built into the garage door itself. They require additional safety features which manage the message traffic from the home automation network, mostly to ensure that those messages will be ignored under certain specific conditions.
This is why so few of the phone app devices originally available for sale ended up being UL listed after the 2013 and 2016 revisions of UL 325. MyQ is for Chamberlain, the Linear/gocontrol zwave Device is, and I believe there are now a few others. But there are many systems which did not provide any way of addressing the two points listed above. The home automation system just sent the command and assumes that the garage door features will handle all the safety issues. UL felt that was not sufficient for remotes which could operate “unattended”. (Again, argue with them, not with me. 
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It’s probably a choice, just make an informed choice
Most US jurisdictions don’t have a law requiring that you meet the UL standard for your own home (although many do if you are installing equipment for someone else, you are a landlord, you have a daycare business in your home, or you operate under Airbnb or similar service). But you should understand why there is potential difference once you add home automation to a garage door and why the existing garage door safety features probably don’t address all of the “unattended operation” hazards.
And again, this isn’t theoretical. We have had community members who had their own cars damaged when a smartapp operating a simple relay repeatedly tried to close the garage door even though it was hitting the car trunk. 
That won’t happen with the gocontrol device. It might hit the car once, but after that the home automation commands will not be accepted until someone physically in the garage has okayed continued operation.
Obviously each person has to assess these issues for themselves, but in order to do that, you need to know what the issues for unattended operation are.
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